The past several years have seen remarkable improvement in GaN-based High Electron Mobility Transistor (HEMT) technology. Much of this is due to improvements in material growth, device design, and device fabrication. Despite significant improvements in power added efficiencies, it is becoming increasingly clear that GaN HEMTs designed for RF, microwave, millimeter wave power, and power switching applications are severely limited by the ability to dissipate heat and thus must run at significantly reduced power levels, pulse length, and duty cycle.
Recent thermal simulations indicate that the substrate is not the primary source of the thermal impedance; rather it is the ability of the III-nitride semiconductor material layers to locally spread the heat to the surrounding material and substrate due to the extraordinarily high power dissipation density in the near-channel device region (estimated at many megawatts) and the strong reduction in thermal conductivity with increasing temperature. Integrating the capability to locally spread the thermal power dissipated near the channel will have a large impact on overall device performance and allow significant total power output improvements.
Features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.